Ingot mold



Patented June 5, 1928.

uurrao STATES "PA-TENT, OFFICE.

EDWARD R..WILLIAMS, OF LATROBE, PENNSYLVANIA, ASSIGNOB T0 VULCAN MOLD AND IRON COMPANY, OF LATROBE, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

1 10 Drawing.

My invention relates to ingot molds.

It is one object of this invention to produce ingot molds which will, barring accldents" and rough usage, give an unexceptional number of ingots or heats during its life.

Some ingot mold makers pour the ingot molds from molten iron as it comes from the blast furnace without remelting." This direct metal method has some limiting factors. The temperature of the molten 1ro n from the time it leaves the furnace until 1t is poured into the mold becomes lower, which reduces its ability to hold carbon in solution. This carbon or kish, as it is called, comes to the surface and makes it necessary to pour the metal with a bottompour ladle. The temperature of the iron being comparatively low reduces its fluidity, and unless the mold wall is fairly thick, as four inches or more, the metal tends to cold shut or solidify in layers, making a scrap mold. It is therefore almost impossible to make good ingot molds by direct metal method, having a small wall thickness. The chemical analysis of direct metal has very great variations and can not make molds of uniform composition. Its total carbon content is not controllable and depends upon the saturation point of the iron for carbon, this point depending on. the temperature and the percentages of silicon, sulphur, phosphorous, man 'anese and probably oxides. Accordingly direct metal molds are very likely to be ununiform.

Cupola metal for molds is made by melting in a cupola pigiron plus possibly returned scrap and purchased cast. iron scrap. Cupola metal as compared with direct metal has better fluidity due to the'hig'her temperature generally obtaining; better control of the temperature owing to the ease of manipulating the coke ratio in. ashorter period of time; better control of thecomposition,

.as tothe silicon, phosphorous, sul hur, and.

manganese, and as to the carbon y the introduction of steel scrap tolower the total carbon content.

.Molds are scrapped among other re sons because of their fire-cracking,which be ins. Y as fine, hair-like cracks on the inside sur ace of the molds, these cracks developing into r larger cracks whose edges are raised above the original surface of the mold. These Application filed June 20,

moor MOLD.

1927. Serial No. 200,305.

4 cracks tend to hold the ingots while soliditying thus tending to break the molds or prevent the ingots from being extracted.

Another cause of scrapping molds is crack-.

ing due to sudden changes of temperature which require the molds to expand and contract rapidly. This is due to mold metal not being strong enough or the mold wall being thin. Another cause of scrapplng 1s due to the warping of the mold walls.

. trix which oxidizes at first the iron and its metalloids an'd'later the graphite itself. As

the oxides require more room than the original iron did, a permanent growth is made. Also constitutional changes occur ,Which' produce Internal stresses eventually forming internal cracks which help make passages for oxygen penetration. The cracks themselves increase the volume of the mold wall. Graphitization or precipitation of tem er carbon from the cementite (Fe C) WhlCh ,oecupies more room helps the mold' growth.

It. is an object of this invention to pro duce ingot molds in which the said growth 'may' be retarded or reduced. This-may be accomplished'by reducing the size and number of. the graphite flakes, thus minimizing the effects of the said differences in coeflicients of expansion; by more uniformldistribution of the graphite; by changing the form of the graphite from a flat'fiake to very fine curved lamellae' or toiround nodules.

In the preferable practice of my invention, I employ a cupola in which .I add to the metal charge, pig iron, forexample, form 40% to'60% steel scrap, giving, for example, -a total carbon content of 3.10% or less. I prefer the silicon'range to be from .90%- to 1.30%, depending on the total carbon. Test bars made of this metal cast in'gren or dry sand molds and poured' at atmospheric temperature showed a white or mottled fracture up to about a two inch section. If the green or dry sand molds up to about two-inch section are heated, the fracture of the test bar becomes grey, and a definite ratio exists between the size of the section and thetemper-ature to which the' molds must be heated. It the test bars cast in green or dry sand molds are about two inches or more thick and cast at atmospheric temperature, the fracture is completely grey although a light grey. Increasing the section of the test bar from about two inches up to six inches or over, the fracture remains practically the same, and uniform from the outside surface to the center of the bar. As ingot molds generally have a wall section of two inches or more, it is not necessary with my method that the molds in which my ingot molds are made shall be heated.

' The size of the graphite flakes is somewhat dependent upon the temperature at which the met-a1 is melted. It is believed that, if the iron is melted at a temperature exceeding 2730 F., all the graphite is dis' solved and in cooling no graphite nuclei appear to aid the precipitation. Consequently F., the graphite whieh forms when precipitation takes place at about 2000 is in a finely divided state, which enhances the value of the steel scrap addition.

The metal just described when poured into molds shrinks considerably more than ordinary grey iron. This shrinkage is not serious. as an allowance for finish can be made or risers can be used which can be.

-- later removed.

' Photomicro aphic tests of the said metal show eat itferences from regular cast iron.. 11 my metal the graphite is almost nodular and almost evenly distributed, while in regular cast ironit 1s in flat flakes irregularly distributed. Under high magnification the matrix of my mold metal 1s largely pearlitic, while in re ular cast iron there is considerable free errite with. a larger percentage-of graphite which breaks up the continuity of the matrix. To havea true pearliticflmatrix the combined carbon must be at the eutectoidamount of 89%.

2- I *1,e72,47e

However, for practical purposes, the combined carbon in my mold metal may range approximately from .70% to 1.10% without affecting the same very much. The'low'limit shows some free ferrlte plus pearlite in the matrix and the high limit shows some free cementite plus pearlite in the matrix.

A test of my mold metal showed a tensile strength of 40,000 pounds per square inch;

a transverse strength of 4700 pounds on 12- inch centers; a deflection of .17 of an inch in 12 inches; and a Brinell hardness of 228. Thus, the strength and elasticity of my metal is about twice those of ordinary cast llOIl.

Ingot molds made from my metal and ac-' cording to the method described have a.

much longer service than the ordinary cast iron molds. Fire checking, cracking and warping of the molds are very much growth of the metal in the duced. The

molds is deci steel made in my molds will be reduced owing to increased service of the molds and to the im roved surface of the ingots which reduces tie cost of chipping and grinding;

I do not limit my invention to the use of a cupola, as an air furnace, or an electric furnace or equivalent 'ma be used. Possibly direct metal may be use with the addition of moltensteel.

With my method it is not necessary that the molds in which my ingot molds are made whose composition is ferrite plus carbon and other metalloids in such proportion as to produce a pearlitic structure having a com-' bined carbon of .7 0% to 1.10%. In testimony whereof I hereunto aflix my signature.

EDWARD R. WILLIAMS.

edlyreduced. ,The cost of 

